Recommendations on A body disc brakes conversion kits?

I have drums on the front of my 71' 340 Pro street Duster and to put it mildly - they suck.

It's time to upgrade to a disc brakes.

1) what kit do your guys recommend?
2) How do I determine which bolt size I have on the front wheels so I buy the correct kit.

here's one option I've look at:

http://store.summitracing.com/partd...908078+4294908074+4294925080+115&autoview=sku

or this:

http://www.jegs.com/i/Stainless+Steel+Brakes/884/A156/10002/-1

ideas? / recommendations?